Monte Carlo simulation on n-γ density logging using D-T neutron generator

D-T neutron source model is developed according to the neutron spectrum and the neutron angular distribution of D-T reaction. A standard calibration well model is built. The transports of D-T neutron and -ray in the well are simulated using MCNP code. Mixed -spectrum and inelastic -spectrum in the NaI detector are obtained for different distance and different density. The data of the mixed gamma count in the energy range of 2.5 to 4.5 MeV as a function of distance show that the detector should be located in the space of 20-80 cm. The nonlinear relationships between the density and the mixed gamma count are presented. The data of the inelastic gamma count in the energy range of 1.0 to 8.0 MeV as a function of distance show that the detector should be located in the space of 20-40 cm or in the neighborhood of 80 cm. The relationships between the density and the inelastic gamma count can be approximatively expressed as a linear function.